Each autumn, millions of people across the UK receive their annual flu jab. It’s a vital step in preventing serious illness and reducing the spread of influenza. In fact, official data from the UK Health Security Agency estimates that last winter the flu vaccine prevented between 96,000 and 120,000 hospital admissions in England alone. Yet despite its importance, a common concern remains: can the flu jab make you ill?
Our pharmacists explain what’s normal to feel after vaccination, what isn’t, and why the flu jab remains one of the safest ways to protect yourself.
What Happens After You Get the Flu Jab in the UK?
The flu vaccine in the UK works by helping your immune system recognise and fight off the flu virus. Most flu jabs use an inactivated (killed) virus that cannot cause infection. Some nasal spray vaccines for children use a weakened live strain that’s too mild to make healthy people ill.
Mild flu-like symptoms after vaccination are not unusual, but they are not the flu itself. They are a sign your body is building protection.
What’s Normal to Experience After the Flu Jab?
You might feel:
- A sore arm where the injection was given
- Mild headache or tiredness
- Slight fever or aching muscles
These mild flu vaccine symptoms usually settle within two to three days.
When to Speak to a Pharmacist
If your symptoms last longer than three days or include high fever, rash, or significant swelling, you should speak to our pharmacist for advice. They can check whether it’s a reaction or an unrelated infection.
Can the Flu Jab Make You Ill?
No — the flu vaccine cannot give you the flu. The viruses used in the injectable flu jab are completely inactivated, meaning they cannot reproduce in your body.
However, your immune system’s response may cause temporary side effects that feel similar to a mild flu. This is your body practising how to fight the real virus.
Why Some People Feel Unwell After the Jab
You may feel slightly under the weather because your body is producing antibodies. This immune activity can lead to short-term tiredness or aches.
Sometimes, people catch other viruses, such as the common cold, around the same time as their flu jab, which leads to the false impression that the vaccine caused the illness.
Who Might Experience More Side Effects
- People receiving the flu jab for the first time
- Those with a stronger immune response (younger adults, for instance)
- People who were already slightly unwell at the time of vaccination
What Are the Common Flu Vaccine Side Effects?
Most flu vaccine side effects are mild and short-lived. These include:
- Pain, redness, or swelling at the injection site
- Headache
- Slight fever or chills
- Muscle or joint pain
Severe allergic reactions are extremely rare. The NHS monitors all vaccines closely for safety and updates its guidance each year.
How to Manage Mild Side Effects of the Flu Vaccine
- Rest and stay hydrated.
- Use simple pain relief such as paracetamol if needed.
- Apply a cool compress to a sore arm.
If you are concerned, our pharmacists can recommend safe ways to relieve discomfort and confirm whether your symptoms are typical.
How Safe Is the Flu Vaccine?
The flu vaccine safety record is excellent. Every batch used in the UK is tested and approved by the Medicines and Healthcare Products Regulatory Agency (MHRA).
The flu vaccine on the NHS and at private pharmacies is suitable for most adults, including pregnant women and people with chronic conditions.
Getting vaccinated each year protects you and those around you, particularly elderly relatives or those with weakened immune systems.
Who Should Get the Flu Jab?
The NHS recommends annual vaccination for:
- Adults aged 65 and over
- People with chronic heart, lung, or kidney conditions
- Pregnant women
- Carers and frontline healthcare workers
Opting for a private flu jab ensures consistent protection year after year.
When Should You See a Pharmacist About Flu-Like Symptoms?
Most mild post-vaccine symptoms fade quickly, but you should seek advice if you:
- Have a fever above 39°C
- Experience breathing difficulties or chest pain
- Develop a widespread rash or swelling
Our pharmacists can assess whether your symptoms are part of a normal immune response or a sign of something else that needs attention.
Protect Your Health This Flu Season with Touchwood Pharmacy
Even if you had mild flu-like symptoms after the vaccine, the benefits far outweigh the temporary discomfort. Each year, the vaccine is updated to match circulating flu strains, providing the most effective protection available.
Skipping your annual jab increases your risk of severe illness and hospitalisation — especially in winter when flu spreads rapidly.
Book your appointment with our experts at Touchwood Pharmacy for your annual flu vaccination and personalised advice on staying protected this season.
FAQs
Can the flu vaccine make you feel ill afterwards?
You may feel slightly unwell for a day or two after your flu jab, with mild symptoms such as tiredness, a low fever, or muscle aches. These effects are short-lived and show that your immune system is responding to the vaccine, but it does not mean you have the flu.
Why do I get flu-like symptoms after my flu jab?
Flu-like symptoms after vaccination happen because your body is building antibodies to protect against flu. This immune response can cause temporary tiredness, headache, or mild fever, which usually resolves within a couple of days.
How long do flu vaccine side effects last?
Most flu vaccine side effects, such as a sore arm, fatigue, or mild temperature, settle within 48 to 72 hours. If your symptoms last longer or become severe, it’s best to speak with our pharmacist for advice.
Should I still get the flu jab if it made me feel unwell before?
Yes. Even if you experienced mild side effects previously, the benefits of annual flu vaccination outweigh short-term discomfort. Our pharmacist can help monitor or manage any side effects safely during future vaccinations.
Can I catch a cold or flu from someone else after my flu jab?
Yes, but not from the vaccine itself. The flu jab does not contain a live virus that can spread between people. However, you can still catch other circulating viruses like colds or COVID-19 around the same time if exposed.
What should I do if I feel unwell after my flu jab?
Rest, drink plenty of fluids, and use mild pain relief if needed. If you develop a high fever, rash, or symptoms lasting longer than three days, contact our pharmacist for assessment and reassurance.
